package com.yangyang.rpc.registry;

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.CountDownLatch;

import org.apache.zookeeper.KeeperException;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooKeeper;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import io.netty.util.internal.ThreadLocalRandom;

/**
 * 服务发现
 * @author chenshunyang
 *
 */
public class ServiceDiscovery {
	 private static final Logger LOGGER = LoggerFactory.getLogger(ServiceDiscovery.class);
	 
	 private CountDownLatch latch = new CountDownLatch(1);
	 
	 private String registryAddress;

	 private List<String> dataList = new ArrayList<>();
	 
	 public ServiceDiscovery(String registryAddress) {
	        this.registryAddress = registryAddress;

	        ZooKeeper zk = connectServer();
	        if (zk != null) {
	            watchNode(zk);
	        }
	    }

	private void watchNode(final ZooKeeper zk) {
		try {
			List<String> nodeList = zk.getChildren(Constant.ZK_REGISTRY_PATH, new Watcher(){

				@Override
				public void process(WatchedEvent event) {
					if (event.getType()== Event.EventType.NodeChildrenChanged) {
						watchNode(zk);
					}
				}
				
			});
			List<String> dataList = new ArrayList<>();
			for (String node : nodeList) {
				byte[] bytes = zk.getData(Constant.ZK_REGISTRY_PATH+"/"+node, false, null);
				dataList.add(new String(bytes));
			} 
			LOGGER.debug("node data: {}", dataList);
			this.dataList = dataList;
			LOGGER.debug("Service discovery triggered updating connected server node.");
		} catch (KeeperException | InterruptedException e) {
			LOGGER.error("" ,e);
			e.printStackTrace();
		}
	}

	private ZooKeeper connectServer() {
		ZooKeeper zk = null;
		try {
			zk = new ZooKeeper(registryAddress,Constant.ZK_SESSION_TIMEOUT, new Watcher(){

				@Override
				public void process(WatchedEvent event) {
					if (event.getState() == Event.KeeperState.SyncConnected) {
						latch.countDown();
					}
				}
				
			});
			latch.await();
		} catch (Exception e) {
			LOGGER.error("",e);
		}
		return zk;
	}
	
	public String discover(){
		String data = null;
		int size = dataList.size();
		if (size >0) {
			if (size == 1) {
				data = dataList.get(0);
                LOGGER.debug("using only data: {}", data);
			}else{
				 data = dataList.get(ThreadLocalRandom.current().nextInt(size));
	             LOGGER.debug("using random data: {}", data);
			}
		}
		return data;
	}
	 

}
